Rheumatic diseases are characterized by inflammation (e.g., redness and/or heat, swelling, and pain) and loss of function of one or more connecting or supporting structures of the body. These types of diseases affect joints, tendons, ligaments, bones, and muscles. The most common symptoms include, but are not limited to, pain, swelling, and stiffness. Some rheumatic diseases can also involve internal organs. There are more than 100 rheumatic diseases.
Some of the more commonly known rheumatic diseases include juvenile rheumatic arthritis, Kawasaki disease and various forms of arthritis such as rheumatoid arthritis (RA) and osteoarthritis (OA). Juvenile rheumatoid arthritis (JRA) is the most common form of arthritis in childhood, causing pain, stiffness, swelling, and loss of function of the joints. Juvenile rheumatoid arthritis causes joint inflammation and stiffness for more than 6 weeks in a child of 16 years of age or less. The arthritis may be associated with rashes or fevers, and may affect various parts of the body. Rheumatologists classify JRA into three main types (pauciarticular, polyarticular, and systemic) depending on the number of joints involved, the symptoms and the presence or absence of certain antibodies found by a blood test.
Pauciarticular arthritis means that four or fewer joints are affected. Pauciarticular arthritis is the most common form of JRA—about half of all children with JRA have this type. Pauciarticular disease typically affects large joints, such as the knees. Girls under age 8 are most likely to develop this type of JRA.
Polyarticular arthritis means that five or more joints are affected. About 30 percent of all children with JRA have polyarticular disease. The small joints, such as those in the hands and feet, are most commonly involved, but the disease may also affect large joints. Polyarticular JRA often is symmetrical; that is, it affects the same joint on both sides of the body. Some children with polyarticular disease have an antibody in their blood called IgM rheumatoid factor (RF). These children often have a more severe form of the disease, which doctors consider to be similar in many ways to adult rheumatoid arthritis.
The most severe type of JRA is systemic arthritis. Besides joint swelling, the systemic form of JRA is characterized by fever and a light skin rash, and may also affect internal organs such as the heart, liver, spleen, and lymph nodes. Rheumatologists sometimes call it Still's disease. Almost all children with this type of JRA test negative for both RF and antinuclear antibody (ANA). The systemic form affects 20 percent of all children with JRA. A small percentage of these children develop arthritis in many joints and can have severe arthritis that continues into adulthood.
Diagnosis of JRA involves a combination of observation of symptoms and laboratory tests. Doctors usually suspect JRA, along with several other possible conditions, when they see children with persistent joint pain or swelling, unexplained skin rashes and fever, or swelling of lymph nodes or inflammation of internal organs. A diagnosis of JRA also is considered in children with an unexplained limp or excessive clumsiness. Currently, no single test or biomarker can be used to diagnose JRA and its disease severity. A doctor diagnoses JRA by carefully examining the patient and considering the patient's medical history, the results of laboratory tests, and x-rays that help rule out other conditions. Laboratory tests usually measure levels of ANA and erythrocyte sedimentation rate (ESR). However, these types of tests do not provide accurate correlations with disease severity. As such, there is a need for an accurate test to diagnose JRA and especially to determine the severity of JRA.
Kawasaki disease is another type of inflammatory disease that mostly affects children. Kawasaki disease is an illness that involves the skin, mouth, and lymph nodes, and typically affects children who are under the age of 5. The cause of Kawasaki disease is unknown, but if the symptoms are recognized early, children with the disease can fully recover within a few days. If it goes untreated, it can lead to serious complications that can involve the heart. Currently, the primary method of diagnosis of Kawasaki disease is observation of symptoms, which can include severe redness in the eyes; a rash on the child's stomach, chest, and genitals; red, dry, cracked lips; swollen tongue with a white coating and big red bumps; sore, irritated throat; swollen palms of the hands and soles of the feet with a purple-red color; and swollen lymph nodes. Accordingly, there is another need for a method of diagnosing this type of disease and its severity as well.
Adult rheumatic diseases occur in many forms. One common rheumatic disease is arthritis, of which there are many types. Common symptoms of arthritis include: swelling in one or more joints, stiffness around the joints that lasts for at least 1 hour in the early morning, constant or recurring pain or tenderness in a joint, difficulty using or moving a joint normally and warmth and redness in a joint. The most common type of arthritis is osteoarthritis. This type of arthritis affects an estimated 21 million adults in the United States. Osteoarthritis primarily affects cartilage, which is the tissue that cushions the ends of bones within the joint. In osteoarthritis, the cartilage begins to fray and may entirely wear away. Osteoarthritis can cause joint pain and stiffness. Disability results most often when the disease affects the spine and the weight-bearing joints (the knees and hips). Osteoarthritis is a type of non-erosive arthritis.
Yet another type of rheumatic disease is rheumatoid arthritis. This inflammatory disease of the synovium, or lining of the joint, results in pain, stiffness, swelling, joint damage, and loss of function of the joints. Inflammation most often affects joints of the hands and feet and tends to be symmetrical (occurring equally on both sides of the body). This symmetry helps distinguish rheumatoid arthritis from other forms of the disease. Rheumatoid arthritis is a type of erosive arthritis.
As with the juvenile rheumatic diseases, diagnosis of adult rheumatic diseases often involves a combination of observing symptoms and laboratory tests. Such laboratory tests include ANA, C-reactive protein (CRP), complete, complete blood count (CBC), creatinine, erythrocyte sedimentation rate (ESR), hematocrit, RF, urinanalysis, white blood cell count, and x-ray. However, there is no single diagnostic biomarker that can determine the disease severity of rheumatic diseases. Accordingly, there exists a great need for a type of marker that can not only diagnose the existence of a particular inflammatory or rheumatic disease state, but also assess the severity of the disease. Such a diagnostic marker would be very helpful for creating a treatment plan for an individual suffering from such diseases and also be useful to track prognosis following the initiation of a treatment plan.
The invention provided herein addresses these needs by disclosing, inter alia, methods and kits for using a single biomarker, follistatin-like protein-1 (FSTL-1), to assess disease states and/or severity of various inflammatory diseases, including rheumatic diseases.
Follistatin-Like Protein-1 (FSTL-1)
FSTL-1 (also known as FRP or TSC-36) is an extracellular glycoprotein belonging to the BM-40/SPARC/osteonectin family of proteins containing both extracellular calcium-binding and follistatin-like domains. See e.g., U.S. Pat. No. 6,410,232. FSTL-1 was originally cloned from an osteoblastic cell line as a TGF-β inducible gene. M. Shibanuma et al., Eur J Biochem 217, 13 (1993). The protein occurs in two isoforms resulting from differential sialylation. FSTL-1 has been detected in the medium of all osteosarcoma and chondrosarcoma cell lines, and in some cells of the fibroblast lineage. In mice, the highest expression of FSTL-1 has been observed in the lung. J. Mashimo et al., Cancer Lett 113, 213 (1997).
The action of FSTL-1 is unclear, and both proliferative and anti-proliferative effects have been reported. It is thought that FRP may play a role in neuralization during embryogenesis and its expression is upregulated by estrogen. See K. Okabayashi et al., Biochem Biophys Res Commun 254, 42 (Jan. 8, 1999) and T. Ohashi et al., Calcif Tissue Int 61, 400 (November, 1997). In contrast to other BM-40 family members, the extracellular calcium-binding domain of FSTL-1 is non-functional, suggesting that, despite its sequence homology to BM-40, it has evolved clearly distinct properties. H. O. Hambrock et al., Journal of Biological Chemistry 279, 11727 (Mar. 19, 2004). Analysis of prostate cancers has revealed that over-expression of FSTL-1 may be associated with higher metastatic potential. L. Trojan et al., Anticancer Res 25, 183 (January-February, 2005). In contrast, FSTL-1 expression has been extinguished in v-ras-transformed rat fibroblasts, and transfection of FSTL-1 into these cells inhibited in vitro invasion and led to growth inhibition in human lung cancer cells. See I. M. Johnston et al., Oncogene 19, 5348 (Nov. 9, 2000) and K. Sumitomo et al., Cancer Lett 155, 37 (Jul. 3, 2000).
In addition, it has previously been shown that FSTL-1 is highly-upregulated in the joints during the acute phase of collagen-induced arthritis (CIA), most prominently at the junction of synovium and eroding bone, suggesting a role in joint destruction. S. Thornton et al., Clin Immunol 105, 155 (2002).
In 1998, Tanaka et al. cloned FRP from rheumatoid arthritis (RA) synovial tissue and demonstrated the presence of anti-FSTL-1 antibodies in the serum and synovial fluid of RA patients. M. Tanaka et al., International Immunology 10, 1305 (1998). In addition, Tanaka et al. analyzed the mRNA expression and protein expression of FRP in from patients with RA and patients with osteoarthritis (OA) and found that the FRP mRNA expression was higher in RA than in OA synovial samples. Importantly, Tanaka et al. concluded that there was no difference in the protein levels of FRP between these two groups.
Ehara et al. measured mRNA expression of FRP in synovial fluid from patients with RA and patients with OA. They found the mRNA expression of FRP was 2.3 fold higher in the RA patients than in the OA patients. Y. Ehara et al., Clin Exp Rheumatol 22, 707 (2004). Importantly, the authors stated that the FRP may exert a protective effect for joint destruction on synoviocytes.
Other groups have used mass spectroscopy to characterize the expression of a large number of genes to determine whether one or a combination of genes could be used for diagnostic purposes. For example, in WO 2005/032328, over 500 genes are disclosed as part of a mass screening. One of these genes (M285 in Table 1) is FSTL-1. Importantly, the data shows that the levels of FSTL-1 protein decreases in patients with erosive arthritis and also in patients with non-erosive arthritis as compared to healthy (normal) individuals (i.e., without arthritis).
Another publication, WO 2004/0018522 describes measurement of mRNA expression levels for a large number of genes to diagnose or predict multiple sclerosis. FSTL-1 appears in Table 3 and 9, however, only mRNA levels are measured and there is very limited disclosure that connects such expression in multiple sclerosis patients with arthritis (or, by extension, to other rheumatic diseases).
Finally, Miyamae et al. reported that FSTL-1 was a novel pro-inflammatory molecule with an unrecognized role in inflammation. T. Miyamae et al. J. Immunol. 177, 4758 (2006). Importantly, there was no disclosure in this reference that teaches or even suggests using protein levels of FSTL-1 as a biomarker for assessing disease severity in inflammatory diseases. As such, the invention describes a novel diagnostic biomarker that is capable of assessing disease severity in inflammatory and/or rheumatic diseases.
Throughout this specification, various patents, patent applications and other types of publications (e.g., journal articles) are referenced. The disclosure of all patents, patent applications, and publications cited herein are hereby incorporated by reference in their entirety for all purposes.